The practice of this invention is described herein with reference to an AC gas discharge plasma display panel (PDP). However, this invention may also be practiced with DC gas discharge plasma displays and other display technologies including flat panel displays and projection displays. Passive and active matrix displays may be used, especially displays in which gray scale is achieved through multiplexing.
Other display technologies include active matrix electroluminescent displays (ELD), liquid crystal displays (LCD) including active matrix or thin film transistor LCD, passive LCD, and ferroelectric liquid crystal (FLC) displays, for example as disclosed in U.S. Pat. Nos. 5,302,966 (Stewart), 5,652,600 (Khormaei et al.), 6,035,070 (Moon et al.), 6,801,213 (Bergstrom et al.), 6,985,164 (Rogers et al.), 7,119,773 (Kim), and US. Patent Application 2006/007249 (Reddy et al.), all incorporated herein by reference. Contemplated displays also include light-emitting diode displays (LED), organic electroluminescent displays, and organic light-emitting diode (OLED) displays. OLED is also called organic light-emitting display. OLED is divided into molecular electroluminescent (EL) and polymer EL. Molecular OLED is disclosed in the prior art by Eastman Kodak, Pioneer of Japan, and Sanyo of Japan. Polymer OLED is disclosed by Philips of Holland, Dow Chemical, UNIAX, and Cambridge University (UK). OLED may be passive matrix or active matrix. Examples are disclosed in U.S. Pat. Nos. 6,395,328 (May), 6,592,969 (Burroughes et al.), 6,858,324 (Towns et al.), 6,861,799 (Friend et al.), 6,949,291 (Holmes et al.), 6,960,877 (Heeks et al.), 6,992,438 (Burroughes et al.), 7,005,196 (Carter et al.), 7,005,484 (Holmes et al.), 7,008,999 (Ho et al.), 7,023,012 (Grzzi et al.), 7,053,412 (Hack et al.), 7,071,612 (Burroughes et al.), 7,074,884 (Towns et al.), 7,078,251 (Burroughes et al.), and 7,215,306 (Lo), all incorporated herein by reference.
The invention may be practiced with projection displays such as digital micro mirror device (DMD) arrays as disclosed in the prior art by Texas Instruments and others or any other projection display that uses multiplexing to achieve gray scale, for example as disclosed in U.S. Pat. Nos. 5,751,379 (Markandey et al.), 5,986,640 (Baldwin et al.), 6,061,049 (Pettitt et al.), 7,265,766 (Kempf), and 7,446,785 (Hewlett et al.), all incorporated herein by reference.
A plasma display panel (PDP) consists of a grid of addressable cell elements, also called pixels or subpixels. As used herein, pixel means subpixel, cell, or subcell and cell means subcell, pixel, or subpixel. A cell or pixel element is defined by the cross point of a row electrode and a column electrode for a columnar discharge display or a column electrode and two row electrodes for a surface discharge display. In the case of a surface discharge display, a pair of row electrodes (X and Y) are termed scan electrode and sustain electrode. As part of each cell element, there is an ionizable gas. In both columnar discharge and surface discharge PDP displays, at least one electrode is isolated with dielectric from the ionizable gas. When the appropriate voltages are applied to the row and column electrodes, the ionizable gas discharges. The discharge may produce visible light or invisible light such as UV light that excites a phosphor. In either case, the cell only has two states, a “light-emitting” state and a “non-light-emitting” state. In most applications, gray scale is achieved through time multiplexing. In a single video frame, the number of times cells are put into the discharge state is proportional to the input luminance defined by the input video signal. The input luminance is the digitally created video input to a PDP from a video receiver or other source.
A single video field is divided in time into ‘n’ number of weighted subfields, each weighted by a unique number of discharge pulses (or sustain pulses). A subfield consists of an addressing period in which cells are selected to be “light-emitting” or “non-light-emitting” and a sustain period in which cells that have been selected to be “light-emitting” produce light proportional to the number of sustains in the subfield. In practice the number of subfields (n) in a field is limited by various timing constraints including addressing time and sustain time. These in turn may be dependent on various physical attributes of the plasma display panel, including display structure, display resolution, gas composition, gas pressure, and the number of rows to address.